Complexes between sodium (sulfamate-carboxylate)isoprene/ethylene oxide double hydrophilic diblock copolymers (SCIEO) and dodecyltrimethylammonium bromide (DTMAB), as well as quaternized poly(2-vinylpyridine) (QP2VP), were studied in aqueous solutions, at pH 7. The complexes are formed due to electrostatic interactions between the anionic groups of the polyelectrolyte block of the copolymers and the cationic groups of the surfactant or the homopolyelectrolyte. The structure of the complexes was investigated as a function of the mixing ratio of the two components in solution and ionic strength by static, dynamic, and electrophoretic light scattering, atomic force microscopy, and fluorescence spectroscopy. The mass and size of the complexes depend on the mixing ratio between the components. A transition from intrachain to an interchain association was observed for block copolymer/ surfactant complexes. SCIEO/QP2VP complexes were found to respond to increasing concentrations of added salt. Spherical and ellipsoid shaped complexes with a core-shell micellar like structure were formed in the systems studied.